Precision magnetic keyboard switch



y 7, 1966 J. P. JONES, JR 3,251,962

PRECISION MAGNETIC KEYBOARD SWITCH Filed May 17, 1965 3 Sheets-Sheet 1 FIG] INVENTOR. JOHN PAUL JONES, JR.

Wad 0n, 5g, 5%

ATTORNEYS May 17, 1966 J. P. JONES, JR 3,251,962

PRECISION MAGNETIC KEYBOARD swncn Filed May 17, 1965 5 Sheets-Sheet 2 FIG.3

INVENTOR JCHN PAUL JONES,JR.

ATTORNEYS May 17, 1966 J. P. JONES, JR

PRECISION MAGNETIC KEYBOARD SWITCH Filed May 17, 1965 3 Sheets-Sheet 5 KEY MOTION CONTACTS M OPERATED INVENTOR JOHN PAUL JONES,JR.

ATTORNEYS 3,251,962 PRECISION MAGNETIC KEYBOARD SWITCH John Paul Jones, Jr., Wynnewood, Pa, 'assignor to Navigation Computer Corporation, a corporation of Pennsylvania Filed May 17, 1965, Ser. No. 456,091 9 Claims. (Cl. 200-87) stroke is reached. Because of these requirements for identical switch operation throughout a keyboard, magnetically operated keyboard switches have been expensive to manufactnlre, requiring. precision control over the United States Patent magnetic field and the accompanying magnetically operated reed switch assemblies. Such precision controls are incompatible with the usual manufacturing tolerances of the magnets and the switches, and formerly have required careful selection of those manufactured switches and magnets falling within very close tolerance ranges.

It is therefore a primary object of the invention to provide a magnetic keyboard switch which uses the run of the factory tolerances of magnets and switches and yet operates within a very close range of tolerances to close the key upon downward stroke and .to open the switch upon upward stroke.

It is another object of the invention to provide a simple method of adjusting magnetically operated keyboard switches for precision operation.

A general object of the invention is to provide improved magnetically operated keyboard switches, suit-able for use in precision applications where precise stroke distances are required for operation.

Thus in accordance with the present invention a magnetically operated switch assembly is provided which uses a glass enclosed magnetic reed switch and an operating magnet movable relative thereto. Such a keyboard switch has spring bias means for returning the key to a reference position after operation and is manually operated over a stroke of predetermined length. In the switch assembly provided by this invention means is provided for adjustably positioning the magnet relative to the switch, and two adjustments are provided for atfixing the switch and magnet respectively in relative adjustable positions to provide .a first and second operating reference. In this manner each switch may be adjusted,

precisely for operation at the identical position on the downward stroke regardless of variations in magnetic field strength and mechanical positioning of contacts Within .the glass reed switch assembly.

Thus in accordance with another aspect of the invention tolerances of magnetically operated keyboard switches are precisely adjusted by first positioning the reed switch set to align its contacts physically at a first reference position at which the switch is permanently aflixed and thereafter positioning the magnet relative to said switch and the key in a movable magnet actuating assembly so that the contacts are operated at a reference position defined by the predetermined specification of extent of motion of downward stroke of the key switch. A second check with respect to the uniformity of the switch and operability within tolerances is made by withdrawing the movable assembly a third reference position to assure that the switch contacts are returned to their normal conditions so that a definite tolerance range is provided between the positions on the stroke at which the switch is operated and released.

The foregoing and further features of operation and advantages are described throughout the following specification taken in reference to the accompanying drawings, wherein:

FIGURE 1 is a perspective exploded view, partly in section, of a keyboard switch provided in accordance with this invention;

FIGURE 2 is an elevation view, partly in section, taken in the direction 2-2 of FIGURE 1;

FIGURE 3 is a side view of the switch assembly mounted in a keyboard assembly looking in the direction 33 as seen in FIGURE 1;

FIGURE 4 is a perspective view of the means for moving the magnet in exploded sub-assembly form;

FIGURE 5 is a top view, in section, taken from the position 55 shown in FIGURE 1;

FIGURE 6 is a diagrammatic view of the operational characteristics of the switch provided by this invention; and

FIGURE 7 is a schematic view of a key energization circuit.

With reference to the switch assembly shown in the various views, a manual key 10 is provided for mounting within a sloping keyboard panel 11 in side by side position with a plurality of other keys to form for example a typewriter keyboard. This key is returned to a normal predetermined position by an actuating spring bias member 12 which is seated in a depression 14 within a cap assembly 15, which is friction fitted Within a cylindrical case 16. This case is slanted at the lower end for mounting upon a panel 13 by means of a mounting bolt 17 and associated nut 18. For this purpose a mounting tab 28 is provided together with a bolt 17 for affixing the key assembly in a specified position so that the switch lead 19 may extend through a further aperture 20 within the mounting panel 13. A key projection 21 is provided in the cap 15 for mating With the-corresponding slot 22 in the body 16 to align the cap assembly which is snapped into place and is frictionally held by means of a deformable plastic ridge 23. In this position -a first aperture 24 in the cap is provided to permit the shaft 25 of the switch operating assembly to protrude and meet the key 10 for friction fit thereon.

In operation the key shaft 25 is journaled in the slot 24 and the corresponding slot 29 in the lateral divider 33 within the case 16 for axial movement within limits defined as two rubber or urethane bumpers '31 and 32 hit the top cap or the internal divider 33 in the body 16.

The movable shaft 25 has aflixed thereto a plastic body 35 Which serves to carry a cylindrical magnet 36 in frictional contact between extending elastic fingers 37 and 38 which can be spread apart to receive the magnet 36. In this manner the mechanical tolerances on the magnet and the switch assembly are not required to be extremely precise, since the cylindrical magnet 36 will tend to selfcenter within the frictional fit of the mating cylindrical aperture in the plastic body 35. The plastic body 35 also by means of a central aperture 40 concentrically passes over the glass body of a magnetic reed switch 4d and thus holds the magnet with its longitudinally oriented poles in alignment with the switch on an axis parallel thereto a fixed distance away. It is important that the operating bottom end of the magnet 43 be machined rather precisely to provide a flat surface from which the field emanates to extend through the magnetic reeds 46 and 4-7 of the glass reed switch 41 which of themselves extend through opposite ends of the glass envelope and become the end leads 4'8 and 49. 'It is necessary to have this edge of the magnet precisely defined in order to attain exact tolerances with respect to closure of the reed relay contacts 46, 47 when the magnet is positioned alongside at an exact predetermined downward stroke position of the shaft 25.

As may be best seen from FIGURE 2, the magnet 36 is frictionally fit within the plastic body 35 at a position which may be monitored through the end apertures E and 51 respectively in the cap and case assembly. This permits the magnet to be axially adjusted to a point that will determine the exact closure position of the switch contacts 46 and 47 so that every keyboard switch will operate at exactly the same level of depression of the manual key 10.

Because of a considerable variation in manufacturing tolerances of the reed switches 41, the contacts 46 and 4.7 are sealed within the glass assembly in an irregular manner. For this reason an adjustable clamp is formed in 'the tribulation at the bottom terminal 60 of the bolt assembly 17 so that the bottom lead 49 can extend therethrough This permits the glass switch 4 1 to be positioned initially ata first reference position by visual inspection of the position of the contact area of reeds 46 and 47, after which the bottom end 6t? of the bolt assembly 17 is indented by pinching upon the lead to fix the reed switch in its operating position. After this step is accomplished then the magnet 36 is adjusted to the position that just closes the contacts 46 and 47 at the specified distance along the key depression troke.

' These adjustments may be made in the manner shown by the diagram of FIGURE 6, wherein it is noted that the typical key is provided with five thirty-seconds of an inch of key stroke motion. With this amount of motion, it may be specified to provide operation of the contacts or contact closure in the case of the switch shown at that position where seventy-five percent of the stroke is completed. Thus the magnet is adjusted axially by forcing it into place in clamps 37, 38 to provide closure at completion of seventy-five percent of the key stroke. A further operational check upon the contacts is made to assure that the contacts are released within a specified return stroke increment of the magnet. Because of hysteresis of the magnetic reeds, the key must be returned upward to a position past the closure point so that all contacts should be reopened at approximately fifty percent of the stroke. The switch closure region is indicated by the cross-hatched section labelled contact operation. Therefore if any switch does not have its contacts opened at the fifty percent position, it may be rejected and/ or readjusted. It may be recognized that the swtich set may be opened or closed by the key stroke depending upon the position of the magnet.

As shown by the schematic diagram of FIGURE 7, the

keyboard switch 41 may be made to have one-shot characteristics by inclusion of a capacitor 72, chargeable through resistor 71 from the +36 v. direct current source at lead 74. This provides adequate one shot drive current from capacitor 72 to a load 73 of the order to five thousand ohms, when the switch is closed, but will cause negligent current through the resistor '71 from the 36 volt source until the switch has been opened long enough to recharge capacitor 72.

This is a desirable feature in a keyboard array of an electronic typewriter, for example, to avoid jamming when an operator works fast enough to depress one key before the last one is released.

As shown in phantom view of FIGURE 3, the oneshot key assembly can be made completely self-contained with the capacitor 72 and the resistor 71 contained within the casing 16.

It has been evident from the foregoing specification that there is provided in connection with this invention novel magnetic switch structure which permits precise adjustment so that a plurality of keyboard switches can be made inexpensively with standard components to operate in a precise manner. Further in accordance with the invention, simplified methods of adjustment are provided for both manufacturing and checking the operation of a switch assembly to meet precision specifications. Accordingly the state of the art is advanced because of the novel features of this invention which are defined with particularity in the following claims.

What is claimed is: V

1. A magnetically operated switchassembly comprising a magnetically operable reed switch with a set of contacts having a longitudinal axis, a magnet with separated poles, manually operable key means moving the poles of said magnet in a path generally parallel to said axis of the reed switch through a range which closes and opens said contacts, spring bias means for returning said key means to a reference position at which the contacts are unoperated, means movable by said key means holding the magnet for movement along said path with said key mean-s and providing relative movement between the magnet and key means to provide a first adjustable reference position for operating said contacts with said magnet at a first calibrated position along said range, and means adjustably positioning said reed switch in a mov able position along the path of said key means including a clamp holding said reed switch in a selectable position along its axis to provide another adjustable reference position for returning said contacts to their inoperated state whensaid magnet by said spring means is returned from the first position.

2. In a magnetically operated reed key switch set assembly with an axially oriented set of contacts and mounted for actuation by a manual key coupled with a switch actuation assembly with a magnet therein movable over a fixed key stroke length parallel to the axis of the reed switch, apparatus for precisely adjusting stroke tolerances so that a plurality of key switches can be made with like characteristics comprising in combination, adjustable positioning means holding the reed switch assembly for axial variations of contact positioning and clamping means included to permit the contacts to be afiixed in alignment at a first fixed axial reference position, holding means in said actuating assembly for moving the magnet therewith adjacent said fixed reference'point, and frictional means adjustably positioning the magnet in said holding means axially relative to said actuating assembly upon introduction of force between the magnet and holding meansto produce operation of the reed switch contacts by said magnet at a further axial reference position to which the magnet is moved within said stroke length.

3. A switch assembly comprising in combination a reed switch with a set of magnetically operable contacts, means aligning said reed switch along an axis,- means for aifixing said reed switch in a calibrated position along said axis, a manually operable key shaft including an actuating mechanism movable along an axis parallel to the switch axis, and elastic clamping means frictionally holding a magnet in said actuating mechanism for selective movement along the axis by exertion of an external axial force between the key shaft and the magnet to position it in said clamping means so that it operates the switch contacts at a specified degree of motion of said mechanism.

4. A switch assembly comprising in combinationa reed switch with a set of magnetically operable contacts, means aligning said reed switch along an axis, means for aflixing said reed switch in a calibrated position along said axis, a manually operable key shaft including an actuating mechanism movable along an axis parallel to the switch axis, and means frictionally holding a magnet in said actuating mechanism for positioning relative to the I key shaft so that it operates the switch contacts at a specified degree of motion of said mechanism, wherein said means for affixing the reed switch comprises a tubulation indented to retain the switch in said calibrated position.

5. A switch assembly comprising in combination a reed switch with a set of magnetically operable contacts, means aligning said reed switch along an axis, means for affixing said reed switch in a calibrated position along said axis, a manually operable key shaft including an actuating mechanism movable along an axis parallel to the switch axis, and means frictionally holding a magnet in said actuating mechanism for positioning relative to the key shaft so that it operates the switch contacts at a specified degree of motion of said mechanism, wherein the magnet is a cylindrical body, and said means holding the magnet is a resilient body having two clamping members defining a cylindrical matrix frictionally holding said magnet in position.

6. A switch assembly as defined in claim 5, wherein the actuating mechanism comprises a shaft movable along an axis parallel to the switch axis on one side thereof, and a plastic body aflixed on said actuating mechanism and movable therewith and having an aperture therein for moving about the switch along its axis, wherein said matrix holding the magnet is aligned on the opposite side of the switch from said shaft.

7. A switch assembly comprising in combination a reed switch with a set of magnetically operable contacts, means aligning said reed switch along an axis, means for afiixing said reed switch in a calibrated position along said axis, a manually operable key shaft including an actuating mechanism movable along an axis parallel to the switch axis, and means frictionally holding a magnet in said actuating mechanism for positioning relative to the key shaft so that it operates the switch contacts at a specified degree of motion of said mechanism, said switch assembly being housed in a hollow longitudinal plastic body having one end cap near one extremity and a lateral divider near the other extremity each defining apertures therein mating with the key shaft for journalling motion of said actuating mechanism, and having the key shaft extending through the apertures at each end to move the magnet along its path inside said hollow body.

8. A keyboard switch comprising in combination a magnet having longitudinally oriented poles, a spring biased key coupled for moving the poles of the magnet a limited distance along a first axis, means positioning a set of magnetic reed switch contacts along an axis parallel said first axis for operation by said magnet, and elastic clamping means for relatively positioning one pole of the magnet adjacent the contacts along said axis relative to said key to attain precise switch contact operation from said magnet by frictional movement'thereof in said clamping means to operate said contacts at a calibrated position of movement of the key.

9. A switch as defined in claim 8 wherein the magnet is linear having at least said pole positioned adjacent the contacts and presents a flat face perpendicular to the magnet axis, whereby the magnetic field is precisely defined for operation of the switch contacts at an exact stroke position.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Funk et al.: Variable Mode Pushbutton Switch, IBM Technical Disclosure, vol. 6, No. 11, April 1964, page 40.

BERNARD A. GILHEANY, Primary Examiner. B. DOBECK, Assistant Examiner. 

1. A MAGNETICALLY OPERATED SWITCH ASSEMBLY COMPRISING A MAGNETICALLY OPERABLE REED SWITCH WITH A SET OF CONTACTS HAVING A LONGITUDINAL AXIS, A MAGNET WITH SEPARATED POLES, MANUALLY OPERABLE KEY MEANS MOVING THE POLES OF SAID MAGNET IN A PATH GENERALLY PARALLEL TO SAID AXIS OF THE REED SWITCH THROUGH A RANGE WHICH CLOSES AND OPENS AID CONTACTS, SPRING BIAS MEANS FOR RETURNING SAID KEY MEANS TO A REFERENCE POSITION AT WHICH THE CONTACTS ARE UNOPERATED, MEANS MOVABLE BY SAID KEY MEANS HOLDING THE MAGNET FOR MOVEMENT ALONG SAID PATH WITH SAID KEY MEANS AND PROVIDING RELATIVE MOVEMENT BETWEEN THE MAGNET AND KEY MEANS TO PROVIDE A FIRST ADJUSTABLE REFERENCE POSITION FOR OPERATING SAID CONTACTS WITH SAID MAGNET AT A FIRST CALIBRATED POSITION ALONG SAID RANGE, AND MEANS ADJUSTABLY POSITIONING SAID REED SWITCH IN A MOVABLE POSITION ALONG THE PATH OF SAID KEY MEANS INCLUDING A CLAMP HOLDING SAID REED SWITCH IN A SELECTABLE POSITION ALONG ITS AXIS TO PROVIDE ANOTHER ADJUSTABLE REFERENCE POSITION FOR RETURNING SAID CONTACTS TO THEIR INOPERATED STATE WHEN SAID MAGNET BY SAID SPRING MEANS IS RETURNED FROM THE FIRST POSITION. 